The long-term goal of this project is to gain an understanding on the structure/function relationship of the ATP synthase as it relates to mechanism of the ATP synthase. This is particularly important in cardiac tissue since the ATP synthase accounts for majority of ATP made under aerobic conditions. Furthermore, regulation of the ATP synthase in heart has been shown to occur under ischemic conditions. Recently, in a collaborative study, we were able to obtain a 3.0-3.3 A electron density map of the yeast F1 ATPase. This major advance now allows us to ask and answer questions using the full tools of yeast genetics and x-ray crystallography. The studies in this proposal, in part, investigate the molecular impact of mutations in genes encoding subunits of the mitochondrial ATP synthase on the structure and function of the ATP synthase. The first aim of this study tests a hypothesis that assembly of ATP synthase can occur in the absence of key subunits and the resulting complex is responsible of the uncoupling of the mitochondria. The second aim tests the hypothesis for the mechanism of a class of mutations, mgi, isolated in subunits of the ATP synthase. The third aim will utilize x-ray crystallography to obtain a high-resolution structure of the F1-ATPase containing the mgi mutations. The fourth and final aim will test the hypothesis that the natural inhibitor of the ATP synthase prevents the unidirectional rotation of the gamma-subunit. These experiments will provide a further understanding on the structure and function of the ATP synthase, but will also provide important information on the functional consequences of mutations in subunits of the ATP synthase. Ultimately, this project will provide critical information on the regulation of the ATP synthase and the importance of this regulation on the overall capabilities of the cell to provide enough energy as demanded by tissue and organism in both the normal and disease states.